London, Oct 30 Levi Johnston, the father to former Alaska Governor Sarah Palin's grandchild, has revealed that he knows certain secrets that might damage her in unspecified ways.

In a two-part interview with CBS News, Johnston asserted that he knows certain things that might upset Palin, but is holding back because he does not want to hurt her.

"I have things that . . . would get [Mrs Palin] in trouble and could hurt her, will hurt her," Times Online quoted Johnston as saying.

"If I really wanted to hurt her, I could, very easily," he said. "But I'm not going to do it. I'm not going that far," he added.

The 19-year-old ice hockey player had alleged on "The Early Show," that the former Alaska governor used to call Trig, her son with Down syndrome, "retarded baby."

However, the allegation has been strongly dismissed by Palin's staff.

"We have purposefully ignored the mean-spirited, malicious and untrue attacks on our family . . . Trig is our 'blessed little angel', who knows it and is lovingly called that every day of his life," said her office.

Meanwhile, Johnston will pose for Playgirl magazine next month on the day Palin appears on The Oprah Winfrey Show. (ANI)